Sound waves give Science Friday the right frequency

Dan Casmier, chemistry teacher, visualizes sound waves using salt and a stainless steel plate hooked up to a vibrational generator during Science Friday at Great Falls College MSU. The patterns become more complex as the frequency gets higher.(Photo: TRIBUNE PHOTO/JULIA MOSS)Buy Photo

Sound waves stole the show during the Oct. 28 edition of Science Friday.

Dr. Dan Casmier, Great Falls College Montana State University chemistry instructor, demonstrated the patterns formed by sound waves at different frequencies of sound.

The experiment was model after a similar test done in the 1800s by German musician and scientist Ernst Chladni. Chladni moved a violin bow across a plate covered in sand to show how the sand would move in response to the sound waves emitted.

Casmier demonstrated the same concept, but with upgraded materials. Casmier’s iPad was plugged into a vibration generator with a metal rod.

A flat, black plate was attached to the rod, and Casmier poured some salt onto the center of the plate.

The iPad started with low frequencies and the salt reacted by moving into simple arches. As Casmier played higher frequencies, the salt patterns became increasingly complex. By the highest frequency, the salt was vibrating in a honeycomb pattern.

Casmier said this experiment is easily re-created at home by using an old speaker, any dark, flat surface and some table salt. There are several free frequency apps available to download.

The next Science Friday will take place Nov. 4. Casmier said he is still tossing around experiment ideas. He is also planning a grand finale event for the first week of December, barring any objections from the weather. Demonstrations and event times are announced a few days prior to the day of the experiment.